Carburetor step-up



July 22,1941. L. D. BOYCE CARBURETOR STEP-UP "Filed April 1, 1939 INVENTOR LEONARD D. BOYCE ATTORNEY Patented July 22, 1941 UNITED STA Es PATENT OFFICE CARBURETOR STEP-UP Leonard D. Boyce, Maplewood, Mo., assignor to Carter Carburetor Corporation, St. Louis, Mo., a corporation of Delaware Application April 1, 1939, Serial No. 265,462

2 Claims.

This invention relates to carburetors for internal combustion engines and particularly to socalled step-upmechanisms therefor.

' Most automotive carburetors now in use are provided with means for enriching the mixture supplied when the associated engine is subjected to an extra heavy load. Such means may take the form of a device responsive to suction posterior to the throttle for opening an auxiliary metering Jet or for enlarging the effective area of the main metering jet, or the device may be operated mechanically from the throttle valve. The step-up device is ordinarily necessary only under extreme load conditions, and during most driving,

an automobile engine will function to the satisfaction of the driver without this auxiliary fuel. Particularly under relatively high temperature conditions, thefunctioning of the auxiliary or step-updevice may be largely dispensed with. Obviously, operation of the step-up device affects the economical operation of the vehicle.

cylinder l1 communicating through passage ill with the carburetor mixture conduit posterior to throttle 8. A piston i9 is slidable in cylinder l1 and constantly urged upwardly by coiled spring 20. Strap I6 is secured to piston l9 whereby needle l3 reciprocates vertically with the piston responsive to suction conditions in the mixture conduit. The various parts are constructed so that when the engine intake suction drops below a predetermined value, on the order of two inches of mercury, spring 20' will force piston l9 and needle l3 upwardly opening auxiliary orifice memv 23 of the float bowl cover.

Accordingly, it is an object of this invention to provide thermostatic means for restricting or preventing the operation of the step-up device under relatively high temperature conditions.

This object and other more detailed objects hereafter appearing are attained substantially by the device illustrated in the accompanying drawing in which Fig. 1 is a vertical transverse section illustrating a carburetor embodying the invention.

Fig. 2 is a. view of a portion of the structure shown in Fig. 1, taken on line 2-2 of Fig. 1, but with parts in different operative positions.

The carburetor shown includes an air horn I, venturis 2, and outlet portion 3 forming a mixture conduit, the outlet portion being flanged as at B for attachment tothe intake manifold (not shown) of an associated internal combustion engine. A choke valve 5 is mounted in the air horn and a throttle valve 6 is located near the outlet portion. Adjacent the mixture conduitds a bowl 1 within which fuel is maintained at a substantially constant level by the usual needle valve 'mechanism 8 controlled by a float 9.

ber 12 to supply additional fuel to the mixture conduit.

A thermostatic strip 2| of. bi-metal is secured by means of a screw 22 within a recessed portion This thermostatic strip extends immediately above suction piston I9, and before a predetermined under-hood temperature is reached, is in a position as shown by dotted lines in Fig. 2, permitting normal operation of the step-up device. However, when a higher temperature is reached, thermostatic strip 2| will bend downwardly moving an abutment 24 at the end thereof into engagement with suction piston IS. The consequent restriction upon operation of the suction piston varies with the temperature and depends upon the relative strengths of the thermostat and spring 20. Strip 2| prevents operation of the step at extreme temperatures normally reached in summer driving, for instance.

The invention is intended for use with substantially any sort of step-up device which is provided with a member movable with the fuel enriching valve. Also the particular form of the thermostat and various features of the carburetor are not essential- The-exclusive use of all modifications as come within the scope of the appended claims is contemplated.

I claim: a

1. In a carburetor, a mixture conduit, a constant level chamber, a main fuel nozzle leading into said mixture conduit, port means providing constantly open communication between said nozzle and said chamber, a valve for said port means, a device responsive to predetermined high suction in said mixture conduit for moving said valve to a predetermined partially restricting position rel;- ative to in said port means to lean out the mixture supplied by the carburetor, a spring for urgins said valve to a more open position under low suction conditions in said conduit, and a thermostat movable when the temperature is high to a position so as to constitute an abutment for said device to positively prevent opening movement of 5% 2,25o,a9a

said valve, said valve being free of said thermostat when the temperature is low whereby the position of said valve is controlled solely by suction to open said auxiliary valve, in device including a piston actuated by predetermined suction posterior to said throttle to close said auxiliary valve against said spring, and a thermostat mounted adjacentsaid device and adapted to move transversely thereof when the temperature is high and said auxiliary valve is in its most restricting position to a position in the path or said device so as to constitute a positive abutment to prevent open- 10 ing at said auxiliary valve by said spring.

LEONARD D. BOYCE. 

